Suspension forks and/or shock absorbers are often utilized on vehicle suspensions, to absorb energy (e.g. bumps) imparted to the wheels by the terrain on which the vehicle is used. When the vehicle is a bicycle, such as a mountain bike or off-road bicycle, the use of a suspension fork and/or shock absorber allows a rider to traverse rougher terrain, at a greater speed and with less fatigue in comparison to riding a rigid bicycle.
In our earlier '136 patent, a suspension fork having an adjustable pressure-relief valve is described. The valve can be adjusted “on-the-fly” and without the use of tools, since a control knob is positioned external to the suspension fork for easy manipulation by the user.
In our earlier '948 and '751 patents, rear shock absorbers and suspension forks having an inertia valve and a pressure-relief valve are described. However, in these two earlier patents, the threshold pressure at which the pressure-relief valve opens is not adjustable without a damper rebuild that involves using tools to replace the pressure-relief shim stack in the damper with another shim stack having a different thickness/spring rate.
Inertia valve dampers having pressure-relief features may have been suggested in the past, see e.g. U.S. Pat. No. 1,818,141 to Lang; U.S. Pat. No. 1,873,133 to Kindl; and U.S. Pat. No. 1,953,178, also to Kindl. However, in dampers such as these, externally adjustable pressure-relief especially for use during the compression stroke does not appear to have been suggested.
Thus, there is room for improvement within the art of suspension dampers, shock absorbers, suspension forks, and bicycle suspensions.